1. Field of the Invention
The present invention relates to a vehicle headlamp having a single filament bulb or discharge bulb, by which the optimum light irradiation range can be obtained at high-speed running time or in a bad weather.
2. Description of the Related Art
A headlamp of an automobile or the like irradiates usually a front range 2 as shown in FIG. 18. At this time, in order to prevent the light of the headlamp from dazzling driver""s eyes of a vehicle on the opposite lane, in the irradiation range on the opposite lane side, the light from the light source is shielded by a shade or the like (not shown) arranged in the lamp.
If the road surface is irradiated with a strong light of the headlamp when a vehicle travels in the rain, there is a problem that by surface reflection from a road surface 4, a driver of the vehicle cannot confirm the condition of the front road surface very well or gives glare to an oncoming vehicle. Further, when fog is irradiated with a strong luminous flux 6 of the headlamp in the fog, the road surface on the downside of the luminous flux 6 is invisible. Therefore, there is a problem that even a white line on the road (a center line or a lane mark at the edge of the road) cannot be confirmed.
Therefore, in an automobile having a conventional headlamp, in the rain or fog, the light is diffused in the front wide range by a supplementary lamp such as a fog lamp or the like instead of the headlamp, and the front road surface portion on the both sides is mainly irradiated, whereby a driver of the vehicle is easy to see the front road surface and can see very well the road surface portion of the front both sides, and particularly a white line on the road to run on the road by the vehicle. Further, it is sometimes effective to reduce glare toward an oncoming vehicle.
However, there is a problem that provision of the above-mentioned supplementary lamp causes a high cost.
An object of the invention is to provide a headlamp which makes the front road surface portion on the both sides visible in the rain or fog and reduces glare toward an oncoming vehicle even by using only the headlamp without providing the supplementary lamp.
In order to solve the aforesaid problem, according to the first aspect of the invention, in a headlamp in which a light source and a reflection mirror that supports the light source are located in a light chamber comprising a transparent cover and a lamp body, a luminous distribution changing means is provided, which shields a part of light from the light source or changes the reflecting direction of the light, and a part of the front road surface is darkened by the luminous distribution changing means. Hereby, in the rain or fog, luminous flux from the headlamp is weakened by the luminous distribution changing means, and a part of the front road surface is darkened thereby to reduce surface reflection from this portion.
According to the second aspect of the invention, in the first aspect, as the aforesaid luminous distribution changing means, a movable shade that can appear in the front of a reflection mirror portion located upper than the light source is provided. Hereby, in the rain or fog, the movable shade is protruded in the front of the reflection mirror portion, and a part of the light emitted from the light source is shielded by the movable shade, whereby the luminous flux from the headlamp is weakened. Further, a part of the front road surface is darkened thereby to reduce the surface reflection from this portion.
According to the third aspect of the invention, a light extracting hole is provided for the reflection mirror portion located upper than the light source, and a movable reflector that can open and close the light extracting hole is provided as the aforesaid luminous distribution changing means. Hereby, in the rain or fog, the light extracting hole is opened thereby to let a part of the light emitted from the light source go backward of the reflection mirror, so that the luminous flux from the headlamp is weakened, and a part of the front road surface is darkened thereby to reduce the surface reflection from this portion similarly to the first aspect of the invention.
According to the fourth aspect of the invention, in the first aspect, a part of the front road surface is a road surface portion in 20-40 m front of a vehicle. Hereby, in the rain or fog, the luminous flux from the headlamp is weakened by the luminous distribution changing means, and the front road surface in 20-40 m front of the vehicle is darkened thereby to reduce the surface reflection from this portion.
According to the fifth aspect of the invention, in the first aspect, as the aforesaid luminous distribution means, there is provided a moving means that moves the light source to a focal position of the reflection mirror and to a position distant from the focal position. Hereby, in the rain or fog, by separating the light source from the focal point of the reflection mirror, and the light emitted from the light source is diffused to the surroundings, so that a part of the front road surface is darkened thereby to reduce the surface reflection from this portion and to lighten the road surface portion of the both sides.
According to the sixth aspect of the invention, in the first aspect, a reflection part for irradiating a lane mark is provided for a part of the aforesaid reflection mirror, and when a part of the front road surface is darkened by the aforesaid luminous distribution changing means, the reflection light from its reflection part is emitted forward. Hereby, when it is rainy or foggy, even if a part of the front road surface is darkened in order to reduce the surface reflection from a part of the front road surface, the lane mark can be irradiated brightly.
According to the seventh aspect of the invention, in the first aspect, a part of the front road surface is located before a portion in 20 m front of a vehicle. Hereby, when it is rainy or foggy, a portion before the portion in 20 m front of the vehicle is darkened by the luminous distribution changing means thereby to reduce the surface reflection that dazzles the driver""s eyes of the vehicle on the opposite lane